Prior studies on the thermal degradation of sucrose have indicated the formation of trisaccharides, presumed to be kestoses (fructosylsucrose derivatives). The thermal decomposition of sucrose is known to proceed via scission of the glucosidic linkage to form a resonance-stabilized fructosyl cation which may then be subject to nucleophilic attack by oxygens of alcohols present in the reaction mixture. Such transfructosylations have been studied in detail with simple alcohols. The assumption of kestose formation mentioned above is predicated upon the fact that the hydroxyls of untreated sucrose could also act as nucleophiles. The primary hydroxyls are the most likely to act thus, since earlier studies showed that the fructosyl cation reacts more readily with primary than with secondary alcohols.
Bollmann and Schmidt-Berg, International Sugar Journal, Vol. 67,(797), p. 143-146, (1965), heated dry crystalline sucrose at 170.degree. C. and identified, by paper chromatography, thirteen products of which five were non-reducing trisaccharides; one of these being identified as 6-kestose. Most of the literature references to kestoses pertain to their biological origins. These trisaccharides, together with their higher d.p. homologues, are found in a number of flowering plant families, where they constitute precursors of the fructan storage polymers and have been implicated in frosthardiness and osmotic control.
There has also been some recent interest in the enzymic preparation from sucrose of 1-kestose and its higher homologues which are reported to have potential as non-nutritive sweeteners, T. Oku, et al "J. Nutr., 114 (1984), p. 1574-1581; S. C. Ziesenitz et al "Proc. Ann. Meeting, Amer. Inst. Nutr. in J. Nutr., 117, (1987), p. 846-851, and H. Hidaka et al, published United Kingdom patent application No. 2,179,946A, (1987).
Lowary et al, Int. Sugar Journal., 1988, Volume 90, No. 1077, pages 164-167, disclose the thermal degradation of non-crystalline sucrose (sucrose melts). There are also disclosed methods to produce amorphous sucrose by dissolving crystalline sucrose in minimal water and then evaporating the water to form an amorphous sucrose melt.
There has also been substantial work involving the polymerization of various sugars such as dextrose to produce various types of products. Thus, U.S. Pat. No. 2,387,375 discloses the polymerization of certain sugars to produce heterogenous mixtures of polymers having a wide variation in degree of polymerization. The polymerization is conducted in the presence of a catalyst or combination of catalysts, such as metaboric acid. Also, U.S. Pat. No. 3,766,165 discloses the polycondensation of saccharides in the presence of polycarboxylic acid catalysts at reduced pressure. In this patent, glucose or maltose is subjected to anhydrous melt polymerization using an edible acid such as citric acid as a catalyst and cross-linking agent. U.S. Pat. Nos. 4,975,534 and 4,965,354 disclose thermal reactions of a sugar such as glucose with glutamic acid and hydrogen chloride respectively, and U.S. Pat. No. 3,300,474 discloses the formation of sucrose ether copolymerizates by reaction of sucrose in aqueous solution in the presence of an alkaline catalyst.
To Applicants' knowledge, however, the present invention provides for the first time a process for the formation of new trisaccharides (iso-kestoses) by heating acid sucrose melts, and also provides novel fructoglucan polymers resulting from the polymerization of amorphous sucrose.